Improving antifouling properties of poly (ether sulfone) UF membranes with hydrophilic coatings of dopamine and poly(2-dimethylamino) ethyl methacrylate salt to enable water reuse

Membrane fouling is a key challenge that must be addressed to assure sustainable water reuse. Here we show that coating as-received PES membranes with thin films (< 85 nm) made from mixtures of self-polymerizing dopamine (DA) and antibacterial hydrophilic polymer, poly(2-dimethylamino) ethyl methacrylate salt (PDMAEMA), can provide antifouling properties against feeds that may be encountered in water reuse applications. Coating was confirmed by XPS; we observed an increase in the N1s peak including a shift corresponding to the quaternary ammonium of the PDMAEMA. SEM confirmed that thin films having thickness < 85 nm were formed. Coatings significantly improved membrane wettability, lowering contact angle from 52 to 21, which likely contributed to the antifouling behavior. Permeability of the as-received membrane was preserved when short coating times (similar to 0.5 h) were used, but decreased with increasing reaction time. We evaluated antifouling performance against fermentation effluent, natural organic matter as a model humic-like material, sodium alginate, and BSA as a model protein. Coated membranes offered improved antifouling performance against fermentation effluent, natural organic matter, and sodium alginate. Shorter coating times (1 h or less) offered better performance, in part because the permeability was higher. The performance of the coatings was feed specific; most significantly, the coatings were not antifouling against BSA. Foulant rejection was either maintained or improved by the coatings. Replacing PDMAEMA with the monomer MAEMA formed coatings with high permeability and similar antifouling behavior, which suggests potential to optimize coating formulation. The two-mechanism pore blockage and cake formation model accurately described the entire filtration run, which individual models cannot do.

Automated summary

This study demonstrates the use of thin films made from mixtures of self-polymerizing dopamine (DA) and antibacterial hydrophilic polymer (PDMAEMA) to coat PES membranes, providing antifouling properties for water reuse applications.